It is known to equip a host vehicle with a radar system for detecting objects such as other vehicles proximate to the host vehicle. Such object detection is desirable for detecting, for example, other vehicles in the so called blind spot which is not readily observable by an operator of a vehicle using typical side-view and rear-view mirrors. Such object detection may also be useful to warn the operator of a rapidly approaching vehicle in an adjacent lane, particularly if the operator indicates that a lane-change is about to be executed by, for example, activating a turn-signal indicator. If the host vehicle is towing a trailer, reflections of radar signals by the trailer may cause the system to indicate that a vehicle is present behind the trailer when there is actually only a vehicle forward the trailer. That is, the trailer may act as a reflective surface (i.e. a mirror) for radar energy emitted and detected by a radar sensor. Because of this, the system may sound a false warning indicating that, for example, a vehicle is approaching from the rear when there is actually nothing but some other vehicle traveling forward of the host vehicle and/or forward of the trailer.